This invention relates to emergency evacuation equipment for aircraft and, in particular, to an inflatable aircraft evacuation slide.
The requirement for reliably evacuating airline passengers in the event of an emergency is well known. Emergencies at take-off and landing often demand swift removal of the passengers from the aircraft because of the potential for injuries from fire, explosion, or sinking in water. A conventional method of quickly evacuating a large number of passengers from an aircraft is to provide multiple emergency exits, each of which is equipped with an inflatable evacuation slide. Although evacuation slides permit passengers to quickly and safely descend from the level of the aircraft exit door to the ground, conventional evacuation slides are highly flexible and in some cases will even buckle at the lower xe2x80x9cfootxe2x80x9d end under the weight of large or obese passengers or under the weight of multiple passengers bunched together tightly on the slide. If an evacuation slide buckles sufficiently under the weight of the passenger, the sliding surface may come in contact with the ground, thereby allowing the passengers to strike the hard surface of the ground during their descent. Worse, a buckled sliding surface may cause a passenger to come to rest in a seated position that is too low for the passenger to quickly gain a footing and move away from the foot of the slide. In an emergency situation, a passenger that is slow to exit the foot end of the slide may be struck by the next passenger descending the slide.
Prior art inflatable evacuation slides typically comprise several parallel inflatable tubular members attached together to form the sliding surface of the evacuation slide. Such slide construction is disclosed, for example, in U.S. Pat. No. 3,669,217 to Fisher and U.S. Pat. No. 4,434,870, also to Fisher. Use of multiple parallel tubes creates a rigid sliding surface that for the most part prevents the passenger from striking the hard ground, but at the cost of substantial weight devoted to the multiple tubes and, in any event, many such slides still do not provide sufficient rigidity at the foot end to avoid passengers coming to rest in a position that is too low to allow them to get to their feet quickly and move away from the foot end of the slide.
The requirement that aircraft evacuation slides be made lighter and lighter weight has lead to the current generation aircraft evacuation slides which comprise a pair of relatively large inflatable tubular side rail members with a fabric sliding surface stretched therebetween. Transverse tubes at the head end and the toe end of the slide maintain the side rails in a spaced apart configuration while a plurality of lower truss members in combination with one or more straps provide the needed rigidity for the light weight design. Unfortunately, these lightweight evacuation slides with a membrane sliding surface exacerbate the problems associated with the large or obese passenger potentially striking the ground and/or coming to rest in a position that prevents them from quickly getting to their feet, because the membrane sliding surface is highly flexible under load.
Accordingly, what is needed is a membrane sliding surface evacuation slide having sufficient rigidity and springiness at the foot end to prevent buckling of the foot end and thereby (1) ensure that a sliding passenger will come to rest at the end of the slide sufficiently elevated to quickly gain a footing and move away from the end of the slide; and (2) ensure the sliding surface does not come in contact with the hard surface of the ground.
The present invention comprises an inflatable evacuation slide having a feature to ensure against buckling of the sliding surface under load. In one embodiment, the slide comprises a fabric sliding surface stretched between two lateral side rail tubes. The lateral side rail tubes are supported by a plurality of transverse tubes and transverse trusses such that the side rail tubes maintain the sliding surface in a taut condition suitable for use as a slide. The foot end of the slide includes an additional longitudinal tube extending from the toe end to a position just short of the lowermost transverse truss. This toe end longitudinal tube acts as a pneumatic spring to support a sliding passenger as he or she reaches the extreme toe end of the evacuation slide. Use of a toe end longitudinal tube permits the evacuation slide to be made of a lightweight construction while still providing the necessary springiness at the toe end to ensure that passengers come to the end of the slide with their posteriors at a sufficient elevation to enable them to move quickly to their feet and away from the end of the slide in an emergency situation.